Liquid laundry detergents are popular with the consumers. Despite numerous liquid detergent products on the market, however, a continuous consumer need exists for lower cost without compromising the performance of the detergent, or even providing improved performance at the same cost.
Ethoxylated fatty acid di-esters (hereinafter “EFADs”) may be co-produced with ethoxylated fatty acid mono-ester, as shown in “Group Selectivity of Ethoxylation of Hydroxy Acids” by A. J. O'lenick, Jr., www.zenitech.com/documents/castor-oul.pdf. M. Stjerndahl et. al. disclosed a method of preparing high purity of ethoxylated fatty acid via esterification with excess of Polyethylene glycol in “Synthesis and Chemical Hydrolysis of Surface-Active Esters”, J. of Surfactants and Detergents, Vol 6, No. 4 (October, 2003) pages 311–318. The same method may be used for making high purity of di-ester with excess of fatty acid chloride. U.S. Pat. Nos. 3,884,946 6,300,508 B1 disclose the products of ethoxylated fatty acid including 2.3% or less of di-ester as a by-product. There are patents, such as US 2002/0042352 A1, U.S. Pat. No. 3,232,506, U.S. Pat. No. 6,107,268, U.S. Pat. No. 3,231,505, U.S. Pat. No. 5,279,313, U.S. Pat. No. 5,854,201, WO 96/29389, WO 96/23049, WO 00/31221, and GB 2,141,965A, disclosed of using ethoxylated fatty acid mono-ester for various applications.
EFADs are not generally regarded as detergent surfactants, due to their relatively low HLB values. Furthermore, EFADs have low to none water-solubility. See for instance EP1092761, which discloses the use of EFADS to generate pearly luster—which means that the EFAD is not solubilised. Thus, the laundry detergent art does not provide any motivation and/or expectation of success for inclusion of EFADs into aqueous, isotropic laundry detergent compositions.
The present invention is based at least in part on the discovery that the inclusion of relatively small quantities of EFADs into aqueous laundry detergent compositions boosts the detergent surfactant performance. By virtue of the surprising boosting effect of EFADs the surfactant amount in the formulation can be decreased (resulting in lower cost of manufacture), while maintaining soil removal performance of the detergent, or even improving it on some types of soil. Furthermore, EFADs provide economical de-foaming benefits without adverse effects, such as haziness, caused by a silicone defomer.